The studies being pursued during the present year are designed to further elucidate the basic interrelationships which exist among the central nervous system, the pituitary gland release of LH and FSH, the ovary and the sex steroids positive and negative feedback mechanisms which modulate these events. To this end the studies specifically to be conducted during the period of this grant year are: a) the role of the catecholamines (turnover rates of norepinephrine and dopamine) in affecting the synthesis and release of LHRH and LH; b) the sites of action of estradiol and progesterone in promoting preovulatory-like surges of LH and FSH in ovariectomized rats. These studies will attempt to define some of the neuronal and adenohypophyseal molecular events which proceed and accompany the synthesis and release of LHRH; c) the role of progesterone in "down regulating" estrogen-induced LH surges. Are these steroid effects mediated via changes in estradiol nuclear binding or do they affect catecholamine activation of LHRH synthesis and release. As well, does progesterone alter membrane properties of axons so that exocytotic processes (Ca ions transport etc.) are deleteriously affected; (d) we also will continue our studies on the ovarian secretion of a non-steroidal substance with FSH-inhibiting activity (FSH-IA). In particular, which gonadotropin (LH or FSH) alters the secretion of FSH-IA in ovarian vein blood, how rapidly are these effects manifested and can other alterations in ovarian function (steroid secretion) be correlated with a decline in FSH-IA in ovarian vein plasma.